HTML: The Definitive Guide

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D. The HTML 3.2 DTD

The HTML 3.2 standard is formally defined as an SGML Document Type Definition (DTD). It is from this DTD that the standard is documented, and upon which this book is based. Note that we have reprinted this DTD verbatim and have not attempted to add extensions to it. Where our description and the DTD deviate, assume the DTD is correct.

<!--
        W3C Document Type Definition for the HyperText Markup Language
        version 3.2 as ratified by a vote of W3C member companies.
        For more information on W3C look at URL http://www.w3.org/
        Date: Tuesday January 14th 1997
        Author: Dave Raggett <dsr@w3.org>
        HTML 3.2 aims to capture recommended practice as of early '96
        and as such to be used as a replacement for HTML 2.0 (RFC 1866).
        Widely deployed rendering attributes are included where they
        have been shown to be interoperable. SCRIPT and STYLE are
        included to smooth the introduction of client-side scripts
        and style sheets. Browsers must avoid showing the contents
        of these element Otherwise support for them is not required.
        ID, CLASS and STYLE attributes are not included in this version
        of HTML.
-->
<!ENTITY % HTML.Version
        "-//W3C//DTD HTML 3.2 Final//EN"
        -- Typical usage:
            <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
            <html>
            ...
            </html>
        --
        >
<!--================== Deprecated Features Switch =========================-->
<!ENTITY % HTML.Deprecated "INCLUDE">
<!--================== Imported Names =====================================-->
<!ENTITY % Content-Type "CDATA"
        -- meaning a MIME content type, as per RFC1521
        -->
<!ENTITY % HTTP-Method "GET | POST"
        -- as per HTTP specification
        -->
<!ENTITY % URL "CDATA"
        -- The term URL means a CDATA attribute
           whose value is a Uniform Resource Locator,
           See RFC1808 (June 95) and RFC1738 (Dec 94).
        -->
<!-- Parameter Entities -->
<!ENTITY % head.misc "SCRIPT|STYLE|META|LINK" -- repeatable head elements -->
<!ENTITY % heading "H1|H2|H3|H4|H5|H6">
<!ENTITY % list "UL | OL |  DIR | MENU">
    <!ENTITY % preformatted "PRE | XMP | LISTING">
]]>
<!ENTITY % preformatted "PRE">
<!--================ Character mnemonic entities ==========================-->
<!ENTITY % ISOlat1 PUBLIC
       "ISO 8879-1986//ENTITIES Added Latin 1//EN//HTML">
%ISOlat1;
<!--================ Entities for special symbols =========================-->
<!-- &trade and &cbsp are not widely deployed and so not included here -->
<!ENTITY amp    CDATA "&#38;"   -- ampersand          -->
<!ENTITY gt     CDATA "&#62;"   -- greater than       -->
<!ENTITY lt     CDATA "&#60;"   -- less than          -->
<!--=================== Text Markup =======================================-->
<!ENTITY % font "TT | I | B  | U | STRIKE | BIG | SMALL | SUB | SUP">
<!ENTITY % phrase "EM | STRONG | DFN | CODE | SAMP | KBD | VAR | CITE">
<!ENTITY % special "A | IMG | APPLET | FONT | BASEFONT | BR | SCRIPT | MAP">
<!ENTITY % form "INPUT | SELECT | TEXTAREA">
<!ENTITY % text "#PCDATA | %font | %phrase | %special | %form">
<!ELEMENT (%font|%phrase) - - (%text)*>
<!-- there are also 16 widely known color names although
  the resulting colors are implementation dependent:
   aqua, black, blue, fuchsia, gray, green, lime, maroon,
   navy, olive, purple, red, silver, teal, white, and yellow
 These colors were originally picked as being the standard
 16 colors supported with the Windows VGA palette.
 -->
<!ELEMENT FONT - - (%text)*     -- local change to font -->
<!ATTLIST FONT
    size    CDATA   #IMPLIED    -- [+]nn e.g. size="+1", size=4 --
    color   CDATA   #IMPLIED    -- #RRGGBB in hex, e.g. red: color="#FF0000" --
    >
<!ELEMENT BASEFONT - O EMPTY    -- base font size (1 to 7)-->
<!ATTLIST BASEFONT
    size    CDATA   #IMPLIED    -- e.g. size=3 --
    >
<!ELEMENT BR    - O EMPTY    -- forced line break -->
<!ATTLIST BR
        clear (left|all|right|none) none -- control of text flow --
        >
<!--================== HTML content models ================================-->
<!--
    HTML has three basic content models:
        %text       character level elements and text strings
        %flow       block-like elements e.g. paragraphs and lists
        %bodytext   as %flow plus headers H1-H6 and ADDRESS
-->
<!ENTITY % block
     "P | %list | %preformatted | DL | DIV | CENTER |
      BLOCKQUOTE | FORM | ISINDEX | HR | TABLE">
<!-- %flow is used for DD and LI -->
<!ENTITY % flow "(%text | %block)*">
<!--=================== Document Body =====================================-->
<!ENTITY % body.content "(%heading | %text | %block | ADDRESS)*">
<!ENTITY % color "CDATA" -- a color specification: #HHHHHH @@ details? -->
<!ENTITY % body-color-attrs "
        bgcolor %color #IMPLIED
        text %color #IMPLIED
        link %color #IMPLIED
        vlink %color #IMPLIED
        alink %color #IMPLIED
        ">
<!ELEMENT BODY O O  %body.content>
<!ATTLIST BODY
        background %URL #IMPLIED  -- texture tile for document background --
        %body-color-attrs;  -- bgcolor, text, link, vlink, alink --
        >
<!ENTITY % address.content "((%text;) | P)*">
<!ELEMENT ADDRESS - - %address.content>
<!ELEMENT DIV - - %body.content>
<!ATTLIST DIV
        align   (left|center|right) #IMPLIED -- alignment of following text --
        >
<!-- CENTER is a shorthand for DIV with ALIGN=CENTER -->
<!ELEMENT center - - %body.content>
<!--================== The Anchor Element =================================-->
<!ELEMENT A - - (%text)* -(A)>
<!ATTLIST A
        name    CDATA   #IMPLIED    -- named link end --
        href    %URL    #IMPLIED    -- URL for linked resource --
        rel     CDATA   #IMPLIED    -- forward link types --
        rev     CDATA   #IMPLIED    -- reverse link types --
        title   CDATA   #IMPLIED    -- advisory title string --
        >
<!--================== Client-side image maps ============================-->
<!-- These can be placed in the same document or grouped in a
     separate document although this isn't yet widely supported -->
<!ENTITY % SHAPE "(rect|circle|poly)">
<!ENTITY % COORDS "CDATA" -- comma separated list of numbers -->
<!ELEMENT MAP - - (AREA)*>
<!ATTLIST MAP
    name    CDATA   #IMPLIED
    >
<!ELEMENT AREA - O EMPTY>
<!ATTLIST AREA
    shape   %SHAPE  rect
    coords  %COORDS #IMPLIED  -- defines coordinates for shape --
    href    %URL    #IMPLIED  -- this region acts as hypertext link --
    nohref (nohref) #IMPLIED  -- this region has no action --
    alt     CDATA   #REQUIRED -- needed for non-graphical user agents --
    >
<!--================== The LINK Element ==================================-->
<!ENTITY % Types "CDATA"
        -- See Internet Draft: draft-ietf-html-relrev-00.txt
           LINK has been part of HTML since the early days
           although few browsers as yet take advantage of it.
           Relationship values can be used in principle:
                a) for document specific toolbars/menus when used
                   with the LINK element in the document head:
                b) to link to a separate style sheet
                c) to make a link to a script
                d) by stylesheets to control how collections of
                   html nodes are rendered into printed documents
                e) to make a link to a printable version of this document
                   e.g. a postscript or pdf version
-->
<!ELEMENT LINK - O EMPTY>
<!ATTLIST LINK
        href    %URL    #IMPLIED    -- URL for linked resource --
        rel     %Types  #IMPLIED    -- forward link types --
        rev     %Types  #IMPLIED    -- reverse link types --
        title   CDATA   #IMPLIED    -- advisory title string --
        >
<!--=================== Images ============================================-->
<!ENTITY % Length "CDATA"   -- nn for pixels or nn% for percentage length -->
<!ENTITY % Pixels "NUMBER"  -- integer representing length in pixels -->
<!-- Suggested widths are used for negotiating image size
     with the module responsible for painting the image.
     align=left or right cause image to float to margin
     and for subsequent text to wrap around image -->
<!ENTITY % IAlign "(top|middle|bottom|left|right)">
<!ELEMENT IMG    - O EMPTY --  Embedded image -->
<!ATTLIST IMG
        src     %URL     #REQUIRED  -- URL of image to embed --
        alt     CDATA    #IMPLIED   -- for display in place of image --
        align   %IAlign  #IMPLIED   -- vertical or horizontal alignment --
        height  %Pixels  #IMPLIED   -- suggested height in pixels --
        width   %Pixels  #IMPLIED   -- suggested width in pixels --
        border  %Pixels  #IMPLIED   -- suggested link border width --
        hspace  %Pixels  #IMPLIED   -- suggested horizontal gutter --
        vspace  %Pixels  #IMPLIED   -- suggested vertical gutter --
        usemap  %URL     #IMPLIED   -- use client-side image map --
        ismap   (ismap)  #IMPLIED   -- use server image map --
        >
<!-- USEMAP points to a MAP element which may be in this document
  or an external document, although the latter is not widely supported -->
<!--=================== Java APPLET tag ===================================-->
<!--
  This tag is supported by all Java enabled browsers. Applet resources
  (including their classes) are normally loaded relative to the document
  URL (or <BASE> element if it is defined). The CODEBASE attribute is used
  to change this default behavior. If the CODEBASE attribute is defined then
  it specifies a different location to find applet resources. The value
  can be an absolute URL or a relative URL. The absolute URL is used as is
  without modification and is not effected by the documents <BASE> element.
  When the codebase attribute is relative, then it is relative to the
  document URL (or <BASE> tag if defined).
-->
<!ELEMENT APPLET - - (PARAM | %text)*>
<!ATTLIST APPLET
        codebase %URL     #IMPLIED   -- code base --
        code     CDATA    #REQUIRED  -- class file --
        alt      CDATA    #IMPLIED   -- for display in place of applet --
        name     CDATA    #IMPLIED   -- applet name --
        width    %Pixels  #REQUIRED  -- suggested width in pixels --
        height   %Pixels  #REQUIRED  -- suggested height in pixels --
        align    %IAlign  #IMPLIED   -- vertical or horizontal alignment --
        hspace   %Pixels  #IMPLIED   -- suggested horizontal gutter --
        vspace   %Pixels  #IMPLIED   -- suggested vertical gutter --
        >
<!ELEMENT PARAM - O EMPTY>
<!ATTLIST PARAM
        name    NMTOKEN   #REQUIRED  -- The name of the parameter --
        value   CDATA     #IMPLIED   -- The value of the parameter --
        >
<!--
Here is an example:
    <applet codebase="applets/NervousText"
        code=NervousText.class
        width=300
        height=50>
    <param name=text value="Java is Cool!">
    <img src=sorry.gif alt="This looks better with Java support">
    </applet>
-->
<!--=================== Horizontal Rule ===================================-->
<!ELEMENT HR    - O EMPTY>
<!ATTLIST HR
        align (left|right|center) #IMPLIED
        noshade (noshade) #IMPLIED
        size  %Pixels #IMPLIED
        width %Length #IMPLIED
        >
<!--=================== Paragraphs=========================================-->
<!ELEMENT P     - O (%text)*>
<!ATTLIST P
        align  (left|center|right) #IMPLIED
        >
<!--=================== Headings ==========================================-->
<!--
  There are six levels of headers from H1 (the most important)
  to H6 (the least important).
-->
<!ELEMENT ( %heading )  - -  (%text;)*>
<!ATTLIST ( %heading )
        align  (left|center|right) #IMPLIED
        >
<!--=================== Preformatted Text =================================-->
<!-- excludes images and changes in font size -->
<!ENTITY % pre.exclusion "IMG|BIG|SMALL|SUB|SUP|FONT">
<!ELEMENT PRE - - (%text)* -(%pre.exclusion)>
<!ATTLIST PRE
        width NUMBER #implied -- is this widely supported? --
        >
<![ %HTML.Deprecated [
<!ENTITY % literal "CDATA"
        -- historical, non-conforming parsing mode where
           the only markup signal is the end tag
           in full
        -->
<!ELEMENT (XMP|LISTING) - -  %literal>
<!ELEMENT PLAINTEXT - O %literal>
]]>
<!--=================== Block-like Quotes =================================-->
<!ELEMENT BLOCKQUOTE - - %body.content>
<!--=================== Lists =============================================-->
<!--
    HTML 3.2 allows you to control the sequence number for ordered lists.
    You can set the sequence number with the START and VALUE attributes.
    The TYPE attribute may be used to specify the rendering of ordered
    and unordered lists.
-->
<!-- definition lists - DT for term, DD for its definition -->
<!ELEMENT DL    - -  (DT|DD)+>
<!ATTLIST DL
        compact (compact) #IMPLIED -- more compact style --
        >
<!ELEMENT DT - O  (%text)*>
<!ELEMENT DD - O  %flow;>
<!-- Ordered lists OL, and unordered lists UL -->
<!ELEMENT (OL|UL) - -  (LI)+>
<!--
       Numbering style
    1   arablic numbers     1, 2, 3, ...
    a   lower alpha         a, b, c, ...
    A   upper alpha         A, B, C, ...
    i   lower roman         i, ii, iii, ...
    I   upper roman         I, II, III, ...
    The style is applied to the sequence number which by default
    is reset to 1 for the first list item in an ordered list.
    This can't be expressed directly in SGML due to case folding.
-->
<!ENTITY % OLStyle "CDATA" -- constrained to: [1|a|A|i|I] -->
<!ATTLIST OL -- ordered lists --
        type      %OLStyle   #IMPLIED   -- numbering style --
        start     NUMBER     #IMPLIED   -- starting sequence number --
        compact  (compact)   #IMPLIED   -- reduced interitem spacing --
        >
<!-- bullet styles -->
<!ENTITY % ULStyle "disc|square|circle">
<!ATTLIST UL -- unordered lists --
        type    (%ULStyle)   #IMPLIED   -- bullet style --
        compact (compact)    #IMPLIED   -- reduced interitem spacing --
        >
<!ELEMENT (DIR|MENU) - -  (LI)+ -(%block)>
<!ATTLIST DIR
        compact (compact) #IMPLIED
        >
<!ATTLIST MENU
        compact (compact) #IMPLIED
        >
<!-- <DIR>              Directory list                  -->
<!-- <DIR COMPACT>      Compact list style              -->
<!-- <MENU>             Menu list                       -->
<!-- <MENU COMPACT>     Compact list style              -->
<!-- The type attribute can be used to change the bullet style
     in unordered lists and the numbering style in ordered lists -->
<!ENTITY % LIStyle "CDATA" -- constrained to: "(%ULStyle|%OLStyle)" -->
<!ELEMENT LI - O %flow -- list item -->
<!ATTLIST LI
        type    %LIStyle     #IMPLIED   -- list item style --
        value    NUMBER      #IMPLIED   -- reset sequence number --
        >
<!--================ Forms ===============================================-->
<!ELEMENT FORM - - %body.content -(FORM)>
<!ATTLIST FORM
        action %URL #IMPLIED  -- server-side form handler --
        method (%HTTP-Method) GET -- see HTTP specification --
        enctype %Content-Type; "application/x-www-form-urlencoded"
        >
<!ENTITY % InputType
        "(TEXT | PASSWORD | CHECKBOX | RADIO | SUBMIT
            | RESET | FILE | HIDDEN | IMAGE)">
<!ELEMENT INPUT - O EMPTY>
<!ATTLIST INPUT
        type %InputType TEXT     -- what kind of widget is needed --
        name  CDATA   #IMPLIED   -- required for all but submit and reset --
        value CDATA   #IMPLIED   -- required for radio and checkboxes --
        checked (checked) #IMPLIED -- for radio buttons and check boxes --
        size CDATA    #IMPLIED   -- specific to each type of field --
        maxlength NUMBER #IMPLIED -- max chars allowed in text fields --
        src   %URL    #IMPLIED   -- for fields with background images --
        align %IAlign #IMPLIED   -- vertical or horizontal alignment --
        >
<!ELEMENT SELECT - - (OPTION+)>
<!ATTLIST SELECT
        name CDATA #REQUIRED
        size NUMBER #IMPLIED
        multiple (multiple) #IMPLIED
        >
<!ELEMENT OPTION - O (#PCDATA)*>
<!ATTLIST OPTION
        selected (selected) #IMPLIED
        value  CDATA  #IMPLIED -- defaults to element content --
        >
<!-- Multi-line text input field. -->
<!ELEMENT TEXTAREA - - (#PCDATA)*>
<!ATTLIST TEXTAREA
        name CDATA #REQUIRED
        rows NUMBER #REQUIRED
        cols NUMBER #REQUIRED
        >
<!--======================= Tables ========================================-->
<!-- Widely deployed subset of the full table standard, see RFC 1942
     e.g. at http://www.ics.uci.edu/pub/ietf/html/rfc1942.txt -->
<!-- horizontal placement of table relative to window -->
<!ENTITY % Where "(left|center|right)">
<!-- horizontal alignment attributes for cell contents -->
<!ENTITY % cell.halign
        "align  (left|center|right) #IMPLIED"
        >
<!-- vertical alignment attributes for cell contents -->
<!ENTITY % cell.valign
        "valign  (top|middle|bottom)  #IMPLIED"
        >
<!ELEMENT table - - (caption?, tr+)>
<!ELEMENT tr - O (th|td)*>
<!ELEMENT (th|td) - O %body.content>
<!ATTLIST table                       -- table element --
        align     %Where;   #IMPLIED  -- table position relative to window --
        width     %Length   #IMPLIED  -- table width relative to window --
        border    %Pixels   #IMPLIED  -- controls frame width around table --
        cellspacing %Pixels #IMPLIED  -- spacing between cells --
        cellpadding %Pixels #IMPLIED  -- spacing within cells --
        >
<!ELEMENT CAPTION - - (%text;)* -- table or figure caption -->
<!ATTLIST CAPTION
        align (top|bottom) #IMPLIED
        >
<!ATTLIST tr                       -- table row --
        %cell.halign;              -- horizontal alignment in cells --
        %cell.valign;              -- vertical alignment in cells --
        >
<!ATTLIST (th|td)                  -- header or data cell --
        nowrap (nowrap)  #IMPLIED  -- suppress word wrap --
        rowspan NUMBER   1         -- number of rows spanned by cell --
        colspan NUMBER   1         -- number of cols spanned by cell --
        %cell.halign;              -- horizontal alignment in cell --
        %cell.valign;              -- vertical alignment in cell --
        width   %Pixels  #IMPLIED  -- suggested width for cell --
        height  %Pixels  #IMPLIED  -- suggested height for cell --
        >
<!--================ Document Head ========================================-->
<!-- %head.misc defined earlier on as "SCRIPT|STYLE|META|LINK" -->
<!ENTITY % head.content "TITLE & ISINDEX? & BASE?">
<!ELEMENT HEAD O O  (%head.content) +(%head.misc)>
<!ELEMENT TITLE - -  (#PCDATA)* -(%head.misc)
          -- The TITLE element is not considered part of the flow of text.
             It should be displayed, for example as the page header or
             window title.
          -->
<!ELEMENT ISINDEX - O EMPTY>
<!ATTLIST ISINDEX
        prompt CDATA #IMPLIED -- prompt message -->
<!--
    The BASE element gives an absolute URL for dereferencing relative
    URLs, e.g.
         <BASE href="http://foo.com/index.html">
         ...
         <IMG SRC="images/bar.gif">
    The image is deferenced to
         http://foo.com/images/bar.gif
   In the absence of a BASE element the document URL should be used.
   Note that this is not necessarily the same as the URL used to
   request the document, as the base URL may be overridden by an HTTP
   header accompanying the document.
-->
<!ELEMENT BASE - O EMPTY>
<!ATTLIST BASE
        href %URL  #REQUIRED
        >
<!ELEMENT META - O EMPTY -- Generic Metainformation -->
<!ATTLIST META
        http-equiv  NAME    #IMPLIED  -- HTTP response header name  --
        name        NAME    #IMPLIED  -- metainformation name       --
        content     CDATA   #REQUIRED -- associated information     --
        >
<!-- SCRIPT/STYLE are place holders for transition to next version of HTML -->
<!ELEMENT STYLE  - - CDATA -- placeholder for style info -->
<!ELEMENT SCRIPT - - CDATA -- placeholder for script statements -->
<!-- ELEMENT STYLE  - - (#PCDATA)*  -(%head.misc) -- style info -->
<!-- ELEMENT SCRIPT - - (#PCDATA)*  -(%head.misc) -- script statements -->
<!--================ Document Structure ===================================-->
<!ENTITY % version.attr "VERSION CDATA #FIXED '%HTML.Version;'.>
<![ %HTML.Deprecated [
    <!ENTITY % html.content "HEAD, BODY, PLAINTEXT?">
]]>
<!ENTITY % html.content "HEAD, BODY">
<!ELEMENT HTML O O  (%html.content)>
<!ATTLIST HTML
        %version.attr; > 
 


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